"Thrift Shop" rapper Macklemore is still looking for a come-up ... because Friday morning he caught a flight on America's favorite bargain airline Southwest ... and TMZ has the pic.

Mack -- real name Ben Haggerty -- boarded the discount flight from Burbank to Las Vegas stuntin' in dark shades, a black jacket, and a hoodie ... and he looked incredible.

We're not judging, but it's always pretty incredible to see famous people on Southwest ... guy really lives up to his reputation.

Now THAT'S a cold ass honkey.